Numerical Simulation Study On Landscape Water Circulation Mode And Anti-seepage Optimization Of Ping’an Mine

In recent years,many places in China have built landscape lakes,and the construction of landscape lakes can provide people with a comfortable and pleasant ecological environment.At present,the biggest problem in landscape lake water is water eutrophication,especially when the landscape lake environment is relatively closed and poor water self-purification ability,this problem is more serious.Affected by human activities,a large number of polluting substances enter the landscape lake,further aggravating the rich nutrition of landscape water.Similarly,the leakage of landscape lake can not be underestimated.The leakage of landscape water on the one hand will cause a large loss of landscape water,on the other hand will cause a series of geological environmental hazards in the surrounding area.In order to ensure the normal operation of the landscape lake,this paper takes the landscape lake of Ping An as the research object.Based on MIKE software,it establishes the two-dimensional hydrodynamic and water quality model and groundwater numerical model respectively,explores the influence of various factors on the circulation water exchange and different leakage on the groundwater,which can provide theoretical basis for the construction,management and operation of the landscape lake in the mining area.Specific research results are as follows:（1）Based on the research results at home and abroad,based on the tracer concentration statistics of Euler method,the water exchange capacity was taken as the evaluation standard of the landscape lake circulating water exchange scheme,and the flow state of the landscape lake was analyzed,and the influence of various factors on the circulating water exchange of the landscape lake was explored.The results show that when the 8#point is taken as the water outlet of the landscape lake,and the surface inlet flow is 0.036m³/s,and the point inlet flow is0.006m³/s,the landscape lake has the best water exchange effect.The average water exchange rate is as high as 80.31%,and the lowest water exchange rate is also 51%.Finally,through the analysis of the influence of wind field on the circulating water exchange of landscape lake,we found that under the south or northerly wind speed of 3.1m/s,the average water exchange rate of landscape lake was slightly reduced compared with the no-wind situation,reduced by 0.95%or1.72%,respectively.Under the southwest wind speed of 3.1m/s,the average water exchange rate of landscape lake is the same as that without wind,and with the increase of wind speed,the overall water exchange rate of landscape lake also increases accordingly.（2）Based on the optimal circulating water exchange scheme under the influence of multiple parameters,the initial water quality of Class V is simulated.The simulation results show that the self-purification capacity of landscape water bodies on different polluting substances varies greatly.After a monthly self-purification effect,the average concentration of NH₄and NO₃decreased by 67%and 54%respectively compared with the initial concentration,meeting the water quality requirements of landscape lake.The average concentration of BOD decreased by26.1%compared with the initial concentration,and the average concentration of PO₄was basically the same as the initial concentration,and did not meet the water quality requirements of the landscape lake.After circulating water exchange on the landscape lake and controlling the concentration of the water intake BOD and PO₄are 5mg/L and 0.05mg/L,respectively,the concentration of BOD and PO₄in the lake can meet the water quality requirements of the landscape lake.Also under the condition of circulating water exchange,the BOD and PO₄concentrations in the lake when the water quality is inferior Class V can be well reduced,which can basically meet the water quality requirements of the landscape lake,and only the concentration of PO₄in some areas was high,which did not meet the water quality requirements.（3）After the impoundment of the landscape lake,the influence of different seepage conditions at the bottom of the lake on the groundwater in the study area was simulated.The simulation results show that if the bottom of the lake is not treated with anti-seepage,the groundwater level in the study area will be greatly raised,with the maximum uplift up to about8m,and the influence range is also wide,up to 1100m,thus causing a series of environmental and geological problems around,and it has a great influence on the subsequent coal mining activities.Geomembrane or bentonite waterproof blanket is used as the impermeable material at the bottom of the lake,and it has no effect on the change of groundwater.However,the use of clay or concrete as impermeable materials at the bottom of the lake has a certain influence on the change of groundwater.At the end of the simulation,the groundwater level in local areas around the landscape lake has been raised by 0.5m and 1.4m,respectively.Finally,through the simulation study of the failure of impervious structures at different locations,it is found that the failure of impervious structures has a greater impact on local regional groundwater,and the closer to the failure point,the greater the relative uplift of groundwater level.The failure range of impervious structures can be determined by setting water level observation Wells around the landscape lake and combining with the simulation method.There are 43 pictures,18 tables and 65 references in this paper.